The present invention relates to a method for phase angle conduction control by means of a monolithically integrated circuit. The invention is particularly directed to circuits in which the instant of generation of the triggering pulse is determined by comparison, in a comparator, between a ramp voltage which is synchronized with the alternating supply, or mains, voltage and which is generated by means of an additionally connected capacitor fed from an internal constant current source of the circuit, and a variable threshold value.
Monolithically integrated phase angle controls are known, in particular for controlling conduction by triacs and thyristors, as disclosed in the German periodical "Elektronik", 1975, issue No. 7, pages 72-74. With the aid of such phase angle control the energy consumption of a load connected to the a.c. mains can be continuously varied by shifting the conduction triggering pulses applied to triacs or thyristors connected ahead of the load between mains voltage phase angles of 0.degree. and 180.degree..
In the prior art, in order to generate triggering pulses in a monolithically integrated phase angle control circuit, a sawtooth generator with constant repetition frequency, which is preferably 100 Hz in a 50 Hz mains and 120 Hz in a 60 Hz mains, provides a voltage which linearly increases in time and the moment of onset of the triggering signal can then be shifted along this ramp by the action of a threshold value switch having a variable response threshold. At the instant when the voltage furnished by the sawtooth generator exceeds the selected response threshold, the threshold value switch activates an output stage which itself contains a pulse generator to produce one triggering pulse of the triggering pulse train. Known phase angle control circuits thus require two timers, i.e. one for the phase shifter to set the triggering instant and one to generate pulses in the output stage.